Applications of supercritical carbon dioxide (critical point 31° C., 7.4 MPa) to the cleaning process of semiconductor devices, as well as MEMS (Micro Electro Mechanical Systems), have been studied (JP07-284739, JP10-50648). Supercritical carbon dioxide can be produced by making the temperature and the pressure of carbon dioxide higher than or equal to the critical point described above. Supercritical carbon dioxide has excellent penetrating and diffusing performance due to the intermediate characteristics between gas and liquid. Therefore, supercritical carbon dioxide easily penetrates into the micro recesses of a wafer in order to entrain and remove foreign objects. In particular, supercritical carbon dioxide easily penetrates into small recesses due to the feature in which there is no surface tension, thus achieving favorable cleaning performance even for a semiconductor device having reduced widths of recesses, which are caused by large-scale integration of the devices etc. Supercritical carbon dioxide is considered as a cleaning medium for the next generation owing to such characteristics.
Further, supercritical carbon dioxide that adheres to recesses can be easily vaporized by depressurizing the chamber that houses a wafer or the like. Studies have been made on using such characteristics and applying supercritical carbon dioxide to the drying process of a wafer and the like.